The present invention relates to a communication control system for conducting control and accounting of data communication in a portable information communication terminal having a radio subscriber portion. In particular, the present invention relates to a technique that is effective when applied to a communication control system for suitably conducting control and accounting of data communication in the event of interruption occurrence of a communication line during data transfer.
Heretofore, data communication using radio communication has been provided. In the current radio communication, however, the radio field intensity rapidly attenuates and the communication line is disconnected in some situations, in such places that radio waves do not reach or hardly reach, such as tunnels or underground markets.
If disconnection of a communication line as described before occurs during data transfer, disconnection processing of data communication is conducted in the communication control apparatus. This results in a problem that data transfer must be conducted from the head of data even in the case where a line is reestablished and data transfer is continued.
And in the current accounting method, there is a problem that accounting is conducted even for data communication that has not been completed. In addition, there is a limit in the number of terminals that can be connected at a time to a radio base station that is conducting radio communication with portable information communication terminals. Even if recovery of a radio wave state is waited and reconnection is attempted after the disconnection of the communication line, therefore, re-connection cannot be achieved immediately. This is also a problem.
In a radio data communication protocol, such as PIAFS (PHS Internet Access Forum Standard) in current radio packet communication and PHS (Personal Handy-phone System), it has become possible to hold logical connection for line disconnection lasting up to 10 and several seconds, automatically reconnects the line after recovery of the radio wave state, and continue data transfer from the interrupted place.
Even if the above described communication protocol is used, however, there still exists the problem that the line is disconnected if the interruption of communication lasts a predetermined time length. In that case, the situation that the above described problems occur remains the same.
As for the problem that data need to be re-transmitted from the head of the data if the line is disconnected during data communication, there is a technique disclosed in JP-A-11-275110, “Radio data communication method and its device”. According to this technique, control data is inserted at the head of transmitted and received data, and data transfer is resumed from the sequel of transferred data after re-establishment of the line.
As for the problem that accounting is conducted even for communication in which data transfer has not been completed, there is a technique disclosed in JP-A-11-69017, “Information distribution system”. According to this technique, the accounting processing is canceled by discriminating interruption of downloading.
As for the problem of connection with a radio base station, there is a technique disclosed in JP-A-9-18930, “Line connection system and line connection method”. According to this technique, a preferential line is secured for a terminal having a high priority order previously assigned thereto, at the time of registration of position information of the pertinent terminal.